Shape-Based approach for full field displacement calculation of cellular materials

In this paper, we propose a new approach of optical full-field measurement for displacement calculation on the surface of a cellular solid. Cell boundary points are sampled as nodes in the analysis. To find the nodal values of displacements the nodes are to be mapped onto their corresponding points in the deformed cell boundary by shape based point matching. A thin plate spline based robust point matching (TPS-RPM) approach is used instead of correlation of intensity pattern between two regions in traditional displacement measurement methods. The proposed approach involves multiple-step image processing including cell region segmentation, cell region matching and node matching. Consequently displacements at a given node can be found easily. Two numerical examples of cellular solids under compressive loading are considered for assessing the effectiveness and accuracy of the proposed algorithm. The results show that local displacements around cell boundaries on the surfaces of the specimen can be effectively determined with the shape based method, thus it appears that the proposed methods is promising for predicting displacements of complex cellular materials.